MC1189656 - Upcoming Change to Teams Desktop Client on Windows

Updated December 17, 2025: January 15, 2026: We are canceling a proposed change related to renaming the existing Calling and Meetings executable.

No action is required from administrators. This change did not introduce a new binary. It involved renaming the existing executable used for Calling and Meetings as a workaround for a Windows compatibility issue. 

What Happened? 

To reduce administrative effort, we partnered with the Windows team to deliver the fix for a Windows compatibility issue. With the Windows fix now fully rolled out in Windows 24H2 and 25H2, the executable name change is no longer required and has been rolled back. 

Was this a security, reliability, or compliance issue? 

• This was not a security or compliance issue. 
• It was a platform compatibility issue in Windows. 
• No customer data, identity, or tenant configuration was at risk. 

Was my tenant impacted? 

Only organizations participating in our Technology Adoption Program (TAP) were affected. Specifically, the change applied only to the TAP Admin earlyadopter subset (Ring 1.5). 

If your organization does not participate in the Microsoft Technology Adoption Program, you were not impacted in any way. The change has been fully rolled back for TAP participants, with no lasting configuration or behavioral changes on client machines. No administrator action is required. 

What if we haven’t deployed recent Windows updates yet? 

We understand that implementingmany enterprises deploy Windows cumulative updates on managed timelines. 

• There is no risk or degradation if the current guidance involves considerable effortreferenced Windows KBs are not installed. 
• New features that depend on these Windows updates will explicitly check for administrators, and we are actively working to reduce this impact. We are exploring ways to make policy changes as seamless as possible, in close partnership with the Windows team.

  Given this ongoing work, we recommend pausing any testing or configuration updates related to this feature. Updated instructions and revised guidance will be shared as partpresence of the formal communication plannedrequired KBs and will only enable when they are available. 

• If the KBs are not installed, those features simply remain disabled—no functionality breaks and no admin action is required. 

Windows updates that include the fix 

The Windows compatibility fix is included in Windows updates for January 2026.versions 24H2 and 25H2, delivered through KB5068861. 

Thank you for the valuable feedback we’ve received. We are currently reassessing the rollout timelinesWhat to ensure alignment with your needs and operational requirements. You can expect a formal update from us by midnext? 

• No changes to late January 2026.admin configuration or tenant settings 
• No service disruption 

---Original message---

Introduction

We’re improving the performance and startup time of calling features in the Microsoft Teams Desktop Client for Windows. To achieve this, we’re introducing a new child process named ms-teams_modulehost.exe that will handle the calling stack separately from the main application process (ms-teams.exe). This change optimizes resource usage and enhances meeting experiences.

Updated rollout timingRollout will be announced inbegin early January 2026 and complete by late January 2026.

Note: Timelines may shift due to year-end feature flag rollout freeze.

• Who is affected: All users running the Teams Desktop Client on Windows.
• What will happen:
  • A new process (ms-teams_modulehost.exe) will appear in Task Manager under the main Teams process (ms-teams.exe).
  • This process is dedicated to calling features and improves performance.
  • No changes to user workflows or UI; however, admins should ensure endpoint and security software allow this new process.

• Update endpoint management and security software to allowlist ms-teams_modulehost.exe alongside ms-teams.exe.
• Communicate this change to helpdesk staff to avoid confusion during troubleshooting.
• Update internal documentation if you reference Teams process names.
• Make sure the same QoS settings applied to ms-teams.exe are also applied to ms-teams_modulehost.exe. Refer to this page for details: Implement Quality of Service (QoS) in Microsoft Teams
  • DO NOT remove QoS settings of ms-teams.exe. Only add QoS settings for ms-teams_modulehost.exe.

No compliance considerations identified, review as appropriate for your organization.